Euv vessel inspection method and related system

ABSTRACT

A single-shot metrology for direct inspection of an entirety of the interior of an EUV vessel is provided. An EUV vessel including an inspection tool integrated with the EUV vessel is provided. During an inspection process, the inspection tool is moved into a primary focus region of the EUV vessel. While the inspection tool is disposed at the primary focus region and while providing a substantially uniform and constant light level to an interior of the EUV vessel by way of an illuminator, a panoramic image of an interior of the EUV vessel is captured by way of a single-shot of the inspection tool. Thereafter, a level of tin contamination on a plurality of components of the EUV vessel is quantified based on the panoramic image of the interior of the EUV vessel. The quantified level of contamination is compared to a KPI, and an OCAP may be implemented.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/883,971, filed Jan. 30, 2018, which claims the benefit of U.S.Provisional Application No. 62/539,273, filed Jul. 31, 2017, theentireties of which are incorporated by reference herein.

BACKGROUND

The electronics industry has experienced an ever increasing demand forsmaller and faster electronic devices which are simultaneously able tosupport a greater number of increasingly complex and sophisticatedfunctions. Accordingly, there is a continuing trend in the semiconductorindustry to manufacture low-cost, high-performance, and low-powerintegrated circuits (ICs). Thus far these goals have been achieved inlarge part by scaling down semiconductor IC dimensions (e.g., minimumfeature size) and thereby improving production efficiency and loweringassociated costs. However, such scaling has also introduced increasedcomplexity to the semiconductor manufacturing process. Thus, therealization of continued advances in semiconductor ICs and devices callsfor similar advances in semiconductor manufacturing processes andtechnology.

As merely one example, semiconductor lithography processes may uselithographic templates (e.g., photomasks or reticles) to opticallytransfer patterns onto a substrate. Such a process may be accomplished,for example, by projection of a radiation source, through an interveningphotomask or reticle, onto the substrate having a photosensitivematerial (e.g., photoresist) coating. The minimum feature size that maybe patterned by way of such a lithography process is limited by thewavelength of the projected radiation source. In view of this, extremeultraviolet (EUV) radiation sources and lithographic processes have beenintroduced. However, EUV systems, which utilize reflective rather thanconventional refractive optics, are very sensitive to contaminationissues. In one example, particle contamination introduced onto surfacesof an EUV vessel (e.g., within which EUV light is generated) can resultin degradation of various components of the EUV vessel. As such, it isnecessary to periodically inspect and perform preventive maintenance(PM) on the EUV vessel. At least some current EUV vessel inspectionmethods utilize a procedure that is merely qualitative and very timeconsuming. This can result in a non-optimal PM schedule, increasedsystem downtime, and reduced system lifetime. Thus, existing EUV vesselinspection techniques have not proved entirely satisfactory in allrespects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of an EUV light source, including anexemplary EUV vessel, in accordance with some embodiments;

FIG. 2A is a top-down view of an EUV vessel, in accordance with someembodiments;

FIG. 2B is an end view of an EUV vessel, according to some embodiments;

FIG. 3A is an exemplary image capture sequence for capturing a pluralityof images as part of a method to image an entirety of an interior of anEUV vessel;

FIG. 3B is a combination image which may be constructed from a pluralityof images captured using the exemplary image capture sequence of FIG.3A;

FIG. 4A is a schematic view of an EUV vessel, in accordance with someembodiments;

FIG. 4B is an exemplary image capture single-shot sequence for imagingan entirety of an interior of an EUV vessel, according to someembodiments;

FIG. 4C is an example image captured using the exemplary image capturesingle-shot sequence of FIG. 4B;

FIG. 5A shows another combination image which may be constructed from aplurality of images captured using the exemplary image capture sequenceof FIG. 3A;

FIG. 5B shows another example of an image captured using the exemplaryimage capture single-shot sequence of FIG. 4B;

FIG. 6 shows a table that provides an exemplary list of EUV vesselcomponents for which KPIs may be defined, and for which OCAPs may beestablished, in accordance with some embodiments;

FIG. 7 is a flow chart of a method for imaging an entirety of aninterior of an EUV vessel using a single camera shot, according to oneor more aspects of the present disclosure; and

FIG. 8 is a schematic view of a lithography system, in accordance withsome embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. Additionally, throughoutthe present disclosure, the terms “mask”, “photomask”, and “reticle” maybe used interchangeably to refer to a lithographic template, such as anEUV mask.

As the minimum feature size of semiconductor integrated circuits (ICs)has continued to shrink, there has continued to be a great interest inphotolithography systems and processes using radiation sources withshorter wavelengths. In view of this, extreme ultraviolet (EUV)radiation sources, processes, and systems (e.g., such as the lithographysystem 800 discussed with reference to FIG. 8) have been introduced.However, EUV systems, which utilize reflective rather than conventionalrefractive optics, are very sensitive to contamination issues. In oneexample, particle contamination introduced onto surfaces of an EUVvessel (e.g., within which EUV light is generated) can result indegradation of various components of the EUV vessel.

Referring to FIG. 1, illustrated therein is a schematic view of an EUVlight source, including an exemplary EUV vessel. In some embodiments, anEUV light source 100 may include a laser produced plasma (LPP) EUV lightsource. Thus, as shown and in some embodiments, the EUV light source 100may include a pulsed laser source 102 (e.g., such as a CO₂ laser) thatgenerates and amplifies a high power laser beam 104. The laser beam 104may then be directed, by a beam transport and focusing system 106, to anEUV vessel 108. In various embodiments, the EUV vessel 108 also includesa droplet generator 110 and a droplet catcher 112. In some cases, thedroplet generator 110 provides droplets of tin or a tin compound intothe EUV vessel 108. In addition, the EUV vessel 108 may include one ormore optical elements such as a collector 114. In some embodiments, thecollector 114 may include a normal incidence reflector, for example,implemented as a multilayer mirror (MLM). For example, the collector 114may include a capping layer (e.g., silicon carbide, SiC) substratecoated with a Mo/Si multilayer. In some cases, one or more barrierlayers may be formed at each interface of the MLM, for example, to blockthermally-induced interlayer diffusion. In some examples, othersubstrate materials may be used for the collector 114 such as Al, Si, orother type of substrate materials. In some embodiments, the collector114 includes an aperture through which the laser beam 104 may passthrough and irradiate droplets generated by the droplet generator 110,thereby producing a plasma at an irradiation region 116. In someembodiments, the collector 114 may have a first focus at the irradiationregion 116 and a second focus at an intermediate focus region 118. Byway of example, the plasma generated at the irradiation region 116produces EUV light 124 collected by the collector 114 and output fromthe EUV vessel 108 through the intermediate focus region 118. Fromthere, the EUV light 124 may be transmitted to an EUV lithography system120 for processing of a semiconductor substrate (e.g., such as discussedwith reference to FIG. 8). In some embodiments, the EUV vessel 108 mayalso include a metrology apparatus 122, as discussed in more detailbelow.

Over time, the collector 114, as well as other interior surfaces 108A ofthe EUV vessel may become contaminated by material from the dropletgenerator 110 (e.g., tin). To maintain optimal performance and extendthe lifetime of the EUV vessel 108, it is necessary to periodicallyinspect and perform preventive maintenance (PM) on the EUV vessel 108.Routine inspection of the EUV vessel 108 may be particularly importantto prevent degradation of the collector 114, for example, and formanagement of various kinds of tin debris. In at least some currentprocesses, deciding when to perform preventive maintenance (e.g., suchas de-clogging the EUV vessel, EUV light collect swap, mirror and/orwindow cleaning), may be based merely on qualitative information that isboth challenging to collect and process. For example, as part of themetrology apparatus 122, a camera adapted to an end of a rod or similarmay be used to capture images of the interior of the EUV vessel 108.

Referring to FIGS. 2A and 2B, illustrated therein are schematic views ofan EUV vessel 200 (e.g., similar to the EUV vessel 108), which providefurther details. For example, FIG. 2A shows a top-down view of the EUVvessel 200 which illustrates a collector (e.g., such as the collector114), a primary focus (e.g., such as the first focus described above),entry of a CO₂ laser (e.g., such as the laser beam 104) through thecollector aperture, and EUV light 202 output from the EUV vessel 200through the intermediate focus region. In some embodiments, the EUVvessel 200 may also include a plurality of vanes. By way of example, theplurality of vanes may be used to assist in the prevention of sourcematerial accumulation (e.g., tin accumulation) on at least some interiorsurfaces of the EUV vessel 200. Thus, in some cases, each of theplurality of vanes may be heated to a melting point of material providedby the droplet generator 110 (e.g., tin) such that the melted materialmay flow (e.g., along a vane fluid channel) into a collection sump.While the vanes may help to reduce at least some EUV vessel 200contamination, periodic inspection and maintenance is neverthelessrequired.

FIGS. 2A and 2B also show a rod 204 having a camera 206 adapted thereto.In some embodiments, the rod 204 and camera 206 may be implemented aspart of a borescope through a port of the EUV vessel 200. FIG. 2B, whichprovides an end-view of the EUV vessel 200, also illustrates a satellitechamber 212 (e.g., coupled to a side of the EUV vessel 200 and to therod 204) and a gate valve 210, for example, through which the borescopepasses. For purposes of this disclosure, and in some cases, the camera206 may be equivalently referred to as an “inspector”. In at least somecurrent methods, and because the camera used has a limited field ofview, a plurality of images are needed in order to adequately image anentirety of an interior of the EUV vessel 200. In other words, existingmethods do not provide for capture of an entirety of an interior of theEUV vessel 200 using a single camera shot. Instead, by rotating and/orextending the rod 204 to which the camera 206 is attached (e.g., asindicated by arrow 208), an entirety of the interior of the EUV vessel200 may be captured, in accordance with at least some existing methods.However, such methods require at least tens of images having differentlevels of backlight illumination. In addition, the field of view of eachimage of the plurality of images is different due to lack of precisemechanical manipulation (e.g., of the rod 204 and/or camera 206). Aftercapture of the plurality of images, a combination image may beconstructed by combining each image of the plurality of images (e.g.,similar to a jigsaw puzzle). However, such a combination image provides,at best, a qualitative characterization of the tin contamination of EUVvessel 200. Thus, without data quantification (e.g., of thecontamination), corresponding defensing and/or preventive measurescannot be adequately prepared. Stated another way, the plurality ofimages collected by such existing methods provide only an indirectinspection technique by attempting to quantify collector tincontamination by measuring an EUV reflection profile from scanner side(e.g., from direction of the EUV lithography system 120 of FIG. 1).

With reference to FIG. 3A, illustrated therein is an exemplary imagecapture sequence 300 (e.g., using the rod 204 and camera 206) forcapturing at least a portion of the plurality of images that may becaptured as part of the method to image an entirety of an interior ofthe EUV vessel 200. In some examples, the image capture sequence 300 maybe used to capture a plurality of images of limited portions (e.g., dueto the limited field of view of the camera 206) of the collector or thelower cone, for example, depending on an orientation and position of therod 204 and the camera 206. As shown in the example of FIG. 3A, theimage capture sequence 300 may include sixteen or more images, asnumbered therein (e.g., for the reflection surface of the collector114). In various cases, each of the plurality of images is captured withthe inspector (e.g., the camera 206) at a different position, such aspositions 302, 304, 306. Of course, many more positions and orientationsmay be needed to capture a completed set of images, in accordance withat least some existing methods. As discussed above, the capturedplurality of images may be used to construct a combination image 310, asshown in FIG. 3B. In the present example, the combination image 310 maybe an image of a collector. From the combination image 310, it is clearthat such a combination image provides, at best, a qualitativecharacterization of contamination.

Generally, for collector tin contamination, at least 50 images (e.g., 50shots) may be required to inspect an entirety of the interior surface ofthe EUV vessel, for example, due to the limited field of view of thecamera/inspector and short distance inside the vessel. This can be avery time-consuming procedure. In addition, such existing methodsrequire a post-data process to construct a combination image, which isalso quite time-consuming. Moreover, as discussed above, thecontamination (e.g., tin contamination) of the EUV vessel cannot bequantified at least because it can be quite difficult to maintain theillumination and the field of view the same for each shot (e.g., foreach image capture). Without data quantification, key performanceindicators (KPIs) cannot be defined, for example, for alarm conditionsand/or for following an out-of-control action plan (OCAP). For EUVvessel tin contamination, the same difficulty is encountered by using aborescope with a limited field of view.

Embodiments of the present disclosure offer advantages over the existingart, though it is understood that other embodiments may offer differentadvantages, not all advantages are necessarily discussed herein, and noparticular advantage is required for all embodiments. For example,embodiments of the present disclosure provide an inspection tool andrelated method that may be used to image an entirety of the EUV vesselusing a single shot. As such, the present disclosure provides asingle-shot method for direct inspection of an entirety of the interiorof the EUV vessel, including providing for quantification ofcontamination (e.g., tin contamination). In some embodiments, thedisclosed inspection tool and single-shot method may be used to image anentirety of an interior of the EUV vessel including a CO₂ mirror (e.g.,a CO₂ laser mirror), an EUV collector, a droplet generation and tincatcher port, a lower cone, vanes (e.g., tin vanes) and a front-sidescrubber, among other components. In various embodiments, the disclosedinspection tool includes a panoramic camera, an illuminator forproviding a uniform and constant light level (e.g., to visualize tindebris), and a vacuum system for camera storage and manipulation. Insome embodiments, the panoramic camera is vacuum compatible. Inaddition, and in some embodiments, the panoramic camera includes twofish-eye camera lenses (e.g., on opposing sides of each other) toprovide a skydome view in a single shot, together with the uniformilluminator. In some embodiments, the disclosed vacuum system includes agate valve and a satellite chamber for camera storage, and a mechanismfor mechanical transport (e.g., a rod) of the camera from the satellitechamber to a primary focus region of the EUV vessel. In variousembodiments, an image processing system may be used to transform thecaptured single-shot skydome view into a plane surface image, afterwhich the EUV vessel contamination can be quantified, for example, bycomparison of a current image to previous images (e.g., for any of aplurality of specified components of the EUV vessel). In some examples,the comparison may be made to an image that conforms to a defined KPIspecification. In various examples, the contamination quantification maybe performed by a local or remote image and/or data processing system.In addition, and because embodiments of the present disclosure providefor quantification of EUV vessel contamination, KPIs of tincontamination for the CO₂ mirror, the EUV collector, the dropletgeneration and tin catcher port, the lower cone, the vanes and thefront-side scrubber can be determined. In some embodiments, KPIs of tincontamination may likewise be determined for other components of the EUVvessel. Further, and as a result of defining the KPIs, an inline monitorof EUV vessel tin contamination can be established and an alarm can beset, thereby providing a defensive system via an advanced datacollection (ADC)/fault detection and classification (FDC) cloud-baseddata system. Thus, embodiments of the present disclosure provide atime-saving approach for EUV vessel inspection by providing for imagingof all EUV vessel components (e.g., such as the collector, the lowercone, the tin vanes, etc.) within an entirety of the interior of the EUVvessel with a single camera shot. Thus, embodiments disclosed hereinprovide for quantification of an amount of various tin contaminants, aswell as collector degradation, within the EUV vessel, thereby enabling acorresponding defensive system and providing for more efficienttroubleshooting. Further, the various embodiments disclosed hereinprovide for tin contamination to be routinely quantified and visualized,which facilitates action plan design (e.g., maintenance) to extend thelifetime of the EUV source vessel and the collector, among other systemcomponents. The disclosed inspection tool and single-shot method canalso significantly reduce the time routinely spent for inspection andpost-data processing by 92%, from about 120 minutes (currently) to lessthan about 10 minutes. Moreover, embodiments of the present disclosurecan be used to increase the weekly tool availability by 1.1% and theproductivity and working hours by nearly 2 hours. Further, variousembodiments disclosed herein provide for improved monitoring and controlof power degradation rate, which can directly impact wafer productivity.Those skilled in the art will recognize other benefits and advantages ofthe methods and inspection tool as described herein, and the embodimentsdescribed are not meant to be limiting beyond what is specificallyrecited in the claims that follow.

Referring now to FIG. 4A, illustrated therein is a schematic view of anEUV vessel 400, in accordance with some embodiments. One or more aspectsof the EUV vessel 400 may be substantially similar to the EUV vessels108, 200, described above. Thus, for the sake of clarity, some featuresmay only be briefly described. As shown in FIG. 4A, the EUV vessel 400may include a droplet generator 410 and a droplet catcher 412, asdescribed above. In various embodiments, the EUV vessel 400 may alsoinclude one or more optical elements such as a collector 422. In someembodiments, the EUV vessel 400 includes a satellite chamber 425 and agate valve 427. In some examples, a panoramic camera 421 including twoopposing fish-eye camera lenses 429, 431 may be mounted to an end of amechanical transport mechanism 433 (e.g., a retractable rod 433). Invarious embodiments, each of the fish-eye camera lenses 429, 431 mayhave an angle of view in a range from about 100 to 180 degrees. Inaddition, and in some cases, an illuminator having a uniform andconstant light level may also be mounted at or near the end of theretractable rod 433 (e.g., adjacent to the panoramic camera). In someembodiments, the satellite chamber 425 is kept under vacuum conditionand is used for camera storage and for protection from tin contamination(e.g., when the gate valve 427 is closed and the retractable rod 433 isretracted). Alternatively, during an inspection process, the gate valve427 may be opened, and the retractable rod 433 is extended to move thepanoramic camera from the satellite chamber 425 to a primary focusregion of the EUV vessel 400. Thereafter, while positioned at theprimary focus region of the EUV vessel 400 and with the illuminatorproviding the uniform and constant light level, a single-shot may betaken by way of the panoramic camera to capture an entirety of theinterior of the EUV vessel 400. By way of example, the fish-eye lens 429may be used to capture a first interior portion of the EUV vessel 400 inthe direction of the collector 422, while the fish-eye lens 431 may beused to capture a second interior portion of the EUV vessel 400 in thedirection of an intermediate focus region 418 (e.g., including the lowercone, vanes, droplet generation and tin catcher port, etc.). Thus, incombination, the dual fish-eye lenses 429, 431 may be used to capture anentirety of the interior of the EUV vessel 400 in a single camera shot.In some embodiments, a full 360 degree panoramic image may beconstructed from the single-shot image captured by the dual fish-eyelenses 429, 431.

With reference to FIG. 4B, illustrated therein is an exemplary imagecapture single-shot sequence 450 (e.g., using the panoramic cameraincluding the two fish-eye camera lenses 429, 431) for imaging anentirety of an interior of the EUV vessel 400 in a single camera shot.In contrast to the image capture sequence 300 described above, the imagecapture sequence 450 includes a single camera shot, where for exampleone of the two fish-eye lenses may be directed toward the collectorwhile the other fish-eye lens is directed to the lower cone. Thus,rather than having to construct a combination image, such as thecombination image 310 of FIG. 3B, embodiments of the present disclosureprovide for a complete imaging of the interior of the EUV vessel 400with a single shot. As one example, FIG. 4C shows an exemplary image 460of a collector of the EUV vessel, taken using the panoramic camera andsingle-shot method disclosed herein. From the image 460, it is clearthat a quantitative characterization of contamination can now beaccurately provided. As a result, KPIs of tin contamination can bedetermined, an inline monitor of EUV vessel tin contamination can beestablished and an alarm can be set, thereby providing a defensivesystem via the ADC/FDC cloud-based data system. As an additionalexample, FIG. 5A shows a combination image 510 (e.g., of a lower coneportion) constructed from a plurality of images, in accordance with atleast some existing methods, and FIG. 5B shows an image 520 of the sameregion shown in FIG. 5A, with the image 520 captured using the panoramiccamera and single-shot method disclosed herein. This side-by-sidecomparison of images serves to further underscore not only thetime-saving advantages provided (e.g., time reduced from about 120minutes to less than 10 minutes), but also the ability to noweffectively quantify tin contamination with the EUV vessel.

As described above, embodiments of the present disclosure provide for adetermination of key performance indicators (KPIs) for a variety of EUVvessel components. As a result of defining the KPIs, an inline monitorof EUV vessel tin contamination can be established and an alarm can beset, thereby providing a defensive system via an ADC/FDC cloud-baseddata system, for example, for alarm conditions and/or for following anOCPA. With reference to FIG. 6, illustrated therein is a table 600 thatprovides an exemplary list of EUV vessel components for which KPIs maybe defined, and for which OCAPs may be established. For example, asshown in row 602 of table 600, a KPI for a CO₂ mirror may be defined asa tin deposition rate %. In this example, after capture andtransformation of the single-shot image into a plane surface image, theCO₂ mirror contamination (e.g., and thus tin deposition rate %) can bequantified and compared to the defined KPI. In some embodiments, thequantification and KPI comparison may be performed by the ADC/FDCcould-based system, which may include an image and/or data processingsystem. Thereafter, based on the results of the KPI comparison and insome embodiments, an OCAP may be implemented. In the present example ofthe CO₂ mirror, the OCAP may include updating the CO₂ mirror lifetimeand estimated PM schedule. In various embodiments, similar proceduresmay be implemented for other defined KPIs. For example, row 604 of table600 illustrates that KPIs for an EUV collector may be defined as ahomogenous tin rate %, a tin drips rate %, and a tin droplet rate %. Forthe example of the EUV collector, the OCAP may include updating thecollector lifetime, determining an EUV throughput, and deciding whetherto troubleshoot the EUV collector. Row 606 of table 600 illustrates thata KPI for a droplet generation port may be defined as a tin depositionrate %, and the OCAP may include updating the EUV vessel and dropletgenerator lifetime, as well as the estimated PM schedule. Row 608 oftable 600 illustrates that a KPI for one or more metrology ports may bedefined as a tin deposition rate %, and the OCAP may include updatingthe metrology port lifetime and the estimated PM schedule. Row 610 oftable 600 illustrates that a KPI for a tin catch port may be defined asa tin deposition rate %, and the OCAP may include updating the EUVvessel lifetime and the estimated PM schedule. Row 612 of table 600illustrates that a KPI for a front-side scrubber may be defined as a tindeposition rate %, and the OCAP may include deciding whether to performan inline thermal de-clogging procedure. Row 614 of table 600illustrates that a KPI for the vanes (e.g., the tin vanes) may bedefined as a tin deposition rate %, and the OCAP may include decidingwhether to perform a thermal cycling process. Row 616 of table 600illustrates that a KPI for the lower cone may be defined as a tindeposition rate %, and the OCAP may include updating the EUV vessellifetime and the estimated PM schedule. While table 600 provided someexamples of EUV vessel components for which KPIs may be defined and forwhich OCAPs may be established, these examples are not meant to belimiting in any way, and it will be understood that other EUV vesselcomponents, other KPIs, and/or other OCAPs may equally be definedwithout departing from the scope of the present disclosure.

Referring now to FIG. 7, illustrated therein are flow chart of a method700 for imaging an entirety of an interior of an EUV vessel using asingle camera shot, according to one or more aspects of the presentdisclosure. It is noted that the process steps of the method 700,including any descriptions given with reference to the figures, aremerely exemplary and are not intended to be limiting beyond what isspecifically recited in the claims that follow. Moreover, additionalprocess steps may be implemented before, during, and after the method700, and some process steps may be replaced or eliminated in accordancewith various embodiments of the method 700.

The method 700 begins at block 702 where an EUV vessel is configuredwith a panoramic camera housed in a satellite chamber coupled to the EUVvessel. By way of example, and in some embodiments, the EUV vessel maybe the EUV vessel 400, as shown in FIG. 4A. As such, in variousembodiments, the EUV vessel may include the satellite chamber 425coupled to an interior of the EUV vessel via the gate valve 427. Inaddition, the panoramic camera may include the two opposing fish-eyecamera lenses 429, 431 which may be mounted to an end of the retractablerod 433. In some cases, an illuminator having a uniform and constantlight level may also be mounted at or near the end of the retractablerod 433. In some cases, the EUV vessel may provide an EUV light sourcefor a lithography system, such as described with reference to FIG. 8.

The method 700 then proceeds to block 704 where the panoramic camera istransversely moved into a primary focus region of the EUV vessel. Forexample, as part of an inspection process of the interior of the EUVvessel, the gate valve 427 may be opened, and the retractable rod 433 isextended to move the panoramic camera from the satellite chamber 425 toa primary focus region of the EUV vessel (e.g., as shown in FIG. 4A).

The method 700 then proceeds to block 706 where a single-shot image ofan entirety of the interior of the EUV vessel is captured. For example,while the panoramic camera is positioned at the primary focus region ofthe EUV vessel and with the illuminator providing the uniform andconstant light level, a single-shot may be taken by way of the panoramiccamera to capture an entirety of the interior of the EUV vessel. In somecases, a first fish-eye lens of the panoramic camera may be used tocapture a first interior portion of the EUV vessel (e.g., in a directionof the collector), while a second fish-eye lens of the panoramic cameramay be used to capture a second interior portion of the EUV vessel(e.g., in a direction of an intermediate focus region). Thus, incombination, the first and second fish-eye lenses may be used to capturean entirety of the interior of the EUV vessel in a single camera shot.

The method 700 then proceeds to block 708 wherein EUV vesselcontamination is quantified and compared to a defined KPI. In someembodiments, the EUV vessel contamination quantification and KPIcomparison may be performed by the ADC/FDC could-based system, which mayinclude an image and/or data processing system, as described above. Atleast some examples of EUV vessel components for which KPIs may bedefined are provided with reference to table 600 of FIG. 6. Thereafter,the method 700 proceeds to block 710 where based on the KPI comparison,an OCAP may be implemented. In various embodiments, the OCAP may includeupdating a lifetime on an EUV vessel component, deciding whether toperform a specific maintenance task, estimating a PM schedule, or otherappropriate actions. Generally, by defining the KPIs and comparing thequantified EUV vessel contamination to the defined KPIs, an inlinemonitor of EUV vessel tin contamination can be established and an alarmcan be set, thereby providing a defensive system via an ADC/FDCcloud-based data system, for example, for alarm conditions and/or forfollowing an OCPA.

As previously noted, the EUV vessel described above may be used toprovide an EUV light source for a lithography system. By way ofillustration, and with reference to FIG. 8, provided therein is aschematic view of an exemplary lithography system 800, in accordancewith some embodiments. The lithography system 800 may also begenerically referred to as a scanner that is operable to performlithographic processes including exposure with a respective radiationsource and in a particular exposure mode. In at least some of thepresent embodiments, the lithography system 800 includes an extremeultraviolet (EUV) lithography system designed to expose a resist layerby EUV light (e.g., provided via the EUV vessel). Inasmuch, in variousembodiments, the resist layer includes a material sensitive to the EUVlight (e.g., an EUV resist). The lithography system 800 of FIG. 8includes a plurality of subsystems such as a radiation source 802 (e.g.,such as the EUV light source 100 of FIG. 1), an illuminator 804, a maskstage 806 configured to receive a mask 808, projection optics 810, and asubstrate stage 818 configured to receive a semiconductor substrate 816.A general description of the operation of the lithography system 800 maybe given as follows: EUV light from the radiation source 802 is directedtoward the illuminator 804 (which includes a set of reflective mirrors)and projected onto the reflective mask 808. A reflected mask image isdirected toward the projection optics 810, which focuses the EUV lightand projects the EUV light onto the semiconductor substrate 816 toexpose an EUV resist layer deposited thereupon. Additionally, in variousexamples, each subsystem of the lithography system 800 may be housed in,and thus operate within, a high-vacuum environment, for example, toreduce atmospheric absorption of EUV light.

In the embodiments described herein, the radiation source 802 may beused to generate the EUV light. In some embodiments, the radiationsource 802 includes a plasma source, such as for example, a dischargeproduced plasma (DPP) or a laser produced plasma (LPP). In someexamples, the EUV light may include light having a wavelength rangingfrom about 1 nm to about 100 nm. In one particular example, theradiation source 802 generates EUV light with a wavelength centered atabout 13.5 nm. Accordingly, the radiation source 802 may also bereferred to as an EUV radiation source 802. In some embodiments, theradiation source 802 also includes a collector, which may be used tocollect EUV light generated from the plasma source and to direct the EUVlight toward imaging optics such as the illuminator 804.

As described above, light from the radiation source 802 is directedtoward the illuminator 804. In some embodiments, the illuminator 804 mayinclude reflective optics (e.g., for the EUV lithography system 800),such as a single mirror or a mirror system having multiple mirrors inorder to direct light from the radiation source 802 onto the mask stage806, and particularly to the mask 808 secured on the mask stage 806. Insome examples, the illuminator 804 may include a zone plate, forexample, to improve focus of the EUV light. In some embodiments, theilluminator 804 may be configured to shape the EUV light passing therethrough in accordance with a particular pupil shape, and including forexample, a dipole shape, a quadrupole shape, an annular shape, a singlebeam shape, a multiple beam shape, and/or a combination thereof. In someembodiments, the illuminator 804 is operable to configure the mirrors(i.e., of the illuminator 804) to provide a desired illumination to themask 808. In one example, the mirrors of the illuminator 804 areconfigurable to reflect EUV light to different illumination positions.In some embodiments, a stage prior to the illuminator 804 mayadditionally include other configurable mirrors that may be used todirect the EUV light to different illumination positions within themirrors of the illuminator 804. In some embodiments, the illuminator 804is configured to provide an on-axis illumination (ONI) to the mask 808.In some embodiments, the illuminator 804 is configured to provide anoff-axis illumination (OAI) to the mask 808. It should be noted that theoptics employed in the EUV lithography system 800, and in particularoptics used for the illuminator 804 and the projection optics 810, mayinclude mirrors having multilayer thin-film coatings known as Braggreflectors. By way of example, such a multilayer thin-film coating mayinclude alternating layers of Mo and Si, which provides for highreflectivity at EUV wavelengths (e.g., about 13.5 nm).

As discussed above, the lithography system 800 also includes the maskstage 806 configured to secure the mask 808. Since the lithographysystem 800 may be housed in, and thus operate within, a high-vacuumenvironment, the mask stage 806 may include an electrostatic chuck(e-chuck) to secure the mask 808. As with the optics of the EUVlithography system 800, the mask 808 is also reflective. As illustratedin the example of FIG. 8, light is reflected from the mask 808 anddirected towards the projection optics 810, which collects the EUV lightreflected from the mask 808. By way of example, the EUV light collectedby the projection optics 810 (reflected from the mask 808) carries animage of the pattern defined by the mask 808. In various embodiments,the projection optics 810 provides for imaging the pattern of the mask808 onto the semiconductor substrate 816 secured on the substrate stage818 of the lithography system 800. In particular, in variousembodiments, the projection optics 810 focuses the collected EUV lightand projects the EUV light onto the semiconductor substrate 816 toexpose an EUV resist layer deposited on the semiconductor substrate 816.As described above, the projection optics 810 may include reflectiveoptics, as used in EUV lithography systems such as the lithographysystem 800. In some embodiments, the illuminator 804 and the projectionoptics 810 are collectively referred to as an optical module of thelithography system 800.

In some embodiments, the lithography system 800 also includes a pupilphase modulator 812 to modulate an optical phase of the EUV lightdirected from the mask 808, such that the light has a phase distributionalong a projection pupil plane 814. In some embodiments, the pupil phasemodulator 812 includes a mechanism to tune the reflective mirrors of theprojection optics 810 for phase modulation. For example, in someembodiments, the mirrors of the projection optics 810 are configurableto reflect the EUV light through the pupil phase modulator 812, therebymodulating the phase of the light through the projection optics 810. Insome embodiments, the pupil phase modulator 812 utilizes a pupil filterplaced on the projection pupil plane 814. By way of example, the pupilfilter may be employed to filter out specific spatial frequencycomponents of the EUV light reflected from the mask 808. In someembodiments, the pupil filter may serve as a phase pupil filter thatmodulates the phase distribution of the light directed through theprojection optics 810.

As discussed above, the lithography system 800 also includes thesubstrate stage 818 to secure the semiconductor substrate 816 to bepatterned. In various embodiments, the semiconductor substrate 816includes a semiconductor wafer, such as a silicon wafer, germaniumwafer, silicon-germanium wafer, III-V wafer, or other type of wafer asdescribed above or as known in the art. The semiconductor substrate 816may be coated with a resist layer (e.g., an EUV resist layer) sensitiveto EUV light. EUV resists may have stringent performance standards. Forpurposes of illustration, an EUV resist may be designed to provide atleast around 22 nm resolution, at least around 2 nm line-width roughness(LWR), and with a sensitivity of at least around 15 mJ/cm². In theembodiments described herein, the various subsystems of the lithographysystem 800, including those described above, are integrated and areoperable to perform lithography exposing processes including EUVlithography processes. To be sure, the lithography system 800 mayfurther include other modules or subsystems which may be integrated with(or be coupled to) one or more of the subsystems or components describedherein.

The various embodiments described herein offer several advantages overthe existing art. It will be understood that not all advantages havebeen necessarily discussed herein, no particular advantage is requiredfor all embodiments, and other embodiments may offer differentadvantages. For example, embodiments discussed herein provide aninspection tool and single-shot method for direct inspection of anentirety of the interior of the EUV vessel, including providing forquantification of contamination (e.g., tin contamination). In variousembodiments, the disclosed inspection tool includes a panoramic camera,an illuminator that provides a uniform and constant light level, and avacuum system for camera storage and manipulation. In some embodiments,the panoramic camera includes two fish-eye camera lenses (e.g., onopposing sides of each other) to provide a skydome view in a singleshot, together with the uniform illuminator. In various embodiments, animage processing system may be used to transform the capturedsingle-shot skydome view into a plane surface image, after which the EUVvessel contamination can be quantified, for example, by comparison of acurrent image to previous images (e.g., for any of a plurality ofspecified components of the EUV vessel). In some examples, thecomparison may be made to an image that conforms to a defined KPIspecification. Based on the results of the KPI comparison and in someembodiments, an OCAP may be implemented. Generally, embodiments of thepresent disclosure provide for an inline monitor of EUV vessel tincontamination and establishment of an alarm system, thereby providing aproactive defense to contamination of the EUV vessel. Thus, embodimentsof the present disclosure serve to overcome various shortcomings of atleast some existing EUV vessel inspection techniques.

Thus, one of the embodiments of the present disclosure described amethod that includes providing a panoramic camera adapted for use withinan extreme ultraviolet (EUV) vessel. In some embodiments, an image of aninterior of the EUV vessel is captured, for example, by way of a singleshot of the panoramic camera. In various examples, and based on theimage of the interior of the EUV vessel, a level of contamination withinthe EUV vessel may then be quantified.

In another of the embodiments, discussed is a method where an EUV vesselincluding an inspection tool integrated with the EUV vessel is provided.In some cases, and during an inspection process, the inspection tool maybe moved into a primary focus region of the EUV vessel. In someembodiments, while the inspection tool is disposed at the primary focusregion and while providing a substantially uniform and constant lightlevel to an interior of the EUV vessel by way of an illuminator, apanoramic image of an interior of the EUV vessel may be captured.Thereafter, in some embodiments, a level of tin contamination on aplurality of components of the EUV vessel may be quantified based on thepanoramic image of the interior of the EUV vessel.

In yet another of the embodiments, discussed is an inspection systemincluding an extreme ultraviolet (EUV) vessel configured for use as partof an EUV light source. In various embodiments, the inspection systemalso includes a satellite chamber coupled to a side of the EUV vessel,where a gate valve is disposed between the satellite chamber and the EUVvessel. In some embodiments, an inspection tool including a panoramiccamera may be coupled to a first end of a mechanical transportmechanism, and a second end of the mechanical transport mechanism may becoupled to a portion of the satellite chamber. In some embodiments, theinspection system further includes an illuminator adjacently coupled tothe panoramic camera. In various examples, the panoramic camera isconfigured, while disposed at a primary focus region of the EUV vessel,to capture an image of a plurality of components of the EUV vessel usinga single shot of the panoramic camera. Moreover, and in someembodiments, the inspection system is configured to quantify, based onthe captured image, a level of tin contamination on the plurality ofcomponents of the EUV vessel.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: capturing, by way of asingle shot of a panoramic camera configured for use within an extremeultraviolet (EUV) vessel, an image of an interior of the EUV vessel,wherein the panoramic camera includes two opposing fish-eye cameralenses; comparing the image to another image that conforms to a definedspecification; and based on the comparing, quantifying a level ofcontamination within the EUV vessel.
 2. The method of claim 1, whereinthe captured image includes an image of an entirety of the interior ofthe EUV vessel.
 3. The method of claim 1, further comprising: whilecapturing the image, providing a substantially uniform and constantlight level to the interior of the EUV vessel.
 4. The method of claim 1,wherein the captured image includes a first image of a collector regionof the EUV vessel and a second image of a lower cone region of the EUVvessel.
 5. The method of claim 4, wherein the first image is captured bya first lens of the two opposing fish-eye camera lenses, and wherein thesecond image is captured by a second lens of the two opposing fish-eyecamera lenses.
 6. The method of claim 1, wherein the captured imageincludes a skydome view image, and wherein the skydome view image istransformed into a plane surface image by an image processing system. 7.The method of claim 6, wherein the comparing the image includescomparing the plane surface image to the another image that conforms tothe defined specification.
 8. The method of claim 1, further comprising:defining a key performance indicator (KPI) for at least one component ofthe EUV vessel; and comparing the quantified level of contaminationwithin the EUV vessel to the KPI.
 9. The method of claim 8, furthercomprising: based on the comparing the quantified level of contaminationwithin the EUV vessel to the KPI, implementing an out-of-control actionplan (OCAP).
 10. The method of claim 9, wherein the OCAP includes one ormore of updating a lifetime of the at least one component of the EUVvessel, performing a maintenance task, and updating an estimatedpreventive maintenance (PM) schedule.
 11. A method, comprising: movingan inspection tool from a storage position to an image capture positionwithin an extreme ultraviolet (EUV) vessel; while the inspection tool isdisposed at the image capture position, capturing an image of anentirety of the interior of the EUV vessel; and after capturing theimage of the entirety of the interior of the EUV vessel, moving theinspection tool from the image capture position to the storage positionwithin the EUV vessel; wherein a level of tin contamination on differentcomponents of the EUV vessel is quantified using the image of theentirety of the interior of the EUV vessel.
 12. The method of claim 11,wherein the different components of the EUV vessel include a CO₂ mirror,an EUV collector, a droplet generation port, a tin catcher port, ametrology port, a lower cone, tin vanes, and a front-side scrubber. 13.The method of claim 11, wherein the inspection process is completed inless than about 10 minutes.
 14. The method of claim 11, wherein thequantified level of tin contamination is determined by comparing theimage of the entirety of the interior of the EUV vessel to at least onepreviously captured image.
 15. The method of claim 11, wherein theinspection tool includes two opposing fish-eye camera lenses.
 16. Aninspection system, comprising: an extreme ultraviolet (EUV) vesselconfigured for use as part of an EUV light source; and an inspectiontool including a panoramic camera retractably coupled to a side of theEUV vessel; wherein the panoramic camera is configured to capture askydome view image of an interior portion of the EUV vessel using asingle shot of the panoramic camera; and wherein an image processingsystem is configured to transform the skydome view image into a planesurface image and quantify a level of tin contamination on the interiorportion of the EUV vessel based on the plane surface image.
 17. Theinspection system of claim 16, wherein the panoramic camera includes twoopposing fish-eye camera lenses.
 18. The inspection system of claim 16,further comprising: a storage chamber coupled to the side of the EUVvessel, wherein the panoramic camera is housed within the storagechamber prior to and after capture of the skydome view image.
 19. Theinspection system of claim 18, wherein the storage chamber preventscontamination of the panoramic camera while the panoramic camera ishoused within the storage chamber.
 20. The inspection system of claim17, wherein a first lens of the two opposing fish-eye camera lenses isconfigured to capture a first portion of the skydome view image thatincludes a collector region; and wherein a second lens of the twoopposing fish-eye camera lenses is configured to capture a secondportion of the skydome view image that includes a lower cone region.